Crankcase ventilation system



April 11, 1967 H. R. SCHNEIDER CRANKCASE VENTILATION SYSTEM Filed March 24, 1965 United States Patent C) Delaware Filed Mar. 24, 1965, Ser. No. 442,366 7 Claims. (Cl. 123119) This invention relates to a crankcase ventilation system for an internal combustion system and, more particularly, to a system of the closed type wherein crankcase vapors are prevented from escaping to atmosphere.

In order to prevent contamination of the atmosphere by unburned hydrocarbons and other contaminants present in the crankcase vapors of internal combustion engines, crankcase ventilation systems have been developed which connect the crankcase with the engine induction system so as to conduct the crankcase vapors into the engine cylinders to be burned. The most generally used of these systems include those in which the crankcase vapors are conducted into the induction system downstream of the carburetor throttling means and those in which the crankcase vapors are conducted into the induction system upstream of the throttling means for instance at the inlet of the air cleaner. In both of these types some sort of valve control is generally required either to control the rate of crankcase vapor flow under varying degrees of manifold vacuum or to prevent the back flow of unfiltered air into the engine crankcase through its connection with the air filter inlet.

It is, therefore, a feature of the present invention that it comprehends a crankcase ventilation system providing for fresh air ventilation of the crankcase without the use of valves or moving parts of any kind.

A further feature of the invention is that the ventilation system prevents the escape to atmosphere of crankcase vapors during all conditions of engine operation.

Another feature of the invention is that it include unrestricted means connecting the crankcase with the induction system so that large volumes of crankcase vapors may be accommodated.

Yet another feature of the invention is that it permits only filtered air to enter the engine crankcase and the engine induction system without the use of one-way valves which would restrict air flow.

These and other features of the invention will be more apparent from the following specification and drawings in which:

FIGURE 1 is a partial side elevation of an internal combustion engine having a crankcase ventilation system according to the present invention and showing the normal operation of the system; and

FIGURE 2 is a partial elevation of the system of FIG- URE 1 showing the operation of the system during a condition of excessive engine blowby.

Referring now to the drawings, an engine generally indicated by numeral 10 includes a crankcase (not shown) communicating at all times through internal passages with rocker compartments partially defined by left bank rocker cover 12 and right bank rocker cover 14, respectively. The engine further includes an induction system comprisin an inlet manifold 16, a carburetor 18 including the usual throttle means 19 and an air cleaner assembly 20 including filtration means 22 and an inlet snorkel 24.

To provide for a normal flow of crankcase vapors into the induction system, tubular means are provided extending between the right bank rocker cover 14 and the air inlet snorkel 24. Such means may comprise a hose 26 connecting with fittings 28 and 30 secured to the cover 14 and snorkel 24, respectively. Baffle means 32 may be provided internally of the cover 14 to separate droplets of oil from the crankcase vapors before they are carried into the induction system.

The invention includes means for admitting ventilating air to the crankcase which are shown as being combined with an oil fill and breather tube 34 mounted on the left bank rocker cover 12. The tube is covered by a breather cap 36 which includes annular filter means 38 through which incoming air must pass. Flow restricting means are provided in the lower portion of the breather tube which, in the present instance, comprise a cup-shaped member 4h retained in the breather cap by spring means 42 and seating against an annular gasket 44 which seals the periphery of member 40 against leakage of air therearound. The member 44) includes a plurality of flow control orifices 46 in the closed end portion thereof through which air passing into the crankcase must pass, as must vapors coming out of the crankcase and into the inlet means. A plurality of openings 48 is also provided in the walls of member 40 to allow air flow therethrough and to provide for engagement with the spring means 42. With this construction, the member 4i} is in operative position whenever the breather cap is properly applied; however, removal of the breather cap also removes member 4-0 so that oil may be added to the engine without requiring it to flow through the control orifices 46.

The breather tube 34 is connected to the induction system downstream of the throttle means by tubular means including a connecting hose St The hose connects with a fitting 52 attached to the fill tube 34 above gasket 44 and connects at its other end with an orifice fitting 54 which is sized to present a predetermined restriction to air flow. Orifice fitting 54 is retained in an adapter plate 56 mounted between the carburetor 18 and inlet manifold 16. However, the fitting could equally well be installed either in the lower portion of the carburetor 18 or in the inlet manifold 16 itself.

The operation of the system under normal engine conditions is indicated by the arrows in FIGURE 1. Air entering the induction system through snorkel 24 creates a pressure reduction which draws crankcase vapors from the right bank rocker cover through tubular means 26, 28, 30 and into the induction air stream in the air filter housing. The reduced pressure in the engine crankcase created by the withdrawal of crankcase vapors draws fresh air from the interior of fill tube 34 through orifices 46 and into the left bank rocker compartment where it mixes with the crankcase vapors and passes through the crankcase into the induction system in the manner previously described. The volume of ventilating air is, of course, limited by the size of the orifices 46.

At the same time, inlet manifold vacuum causes a flow of fresh air to be drawn into filter element 38, and through openings 48, tubular means 59, 52 and orifice fitting 54 into the induction system. The size of the orifice in fitting 54 limits the amount of air flow therethrough to a predetermined value for which the carburetor must be compensated to obtain proper fuel proportions.

Under some conditions, vacuum in the air filter snorkel may be so low or blowby into the engine crankcase may be so high that the normal flow path through tube 26 may not draw from the crankcase all the vapors which tend to collect therein. In such a case, a slight pressure will be created in the crankcase. Vapors will, of course, continue to flow through tube 26 but, in addition, as shown in FIGURE 2, crankcase vapors will also be allowed to pass out of the left bank rocker cover 12 and through orifices 46 to the interior of fill tube 34. There, they will be mixed with the continuous flow of fresh air through filter element 38 and will pass through openings 48, fitting 52, hose 5i and orifice fitting 54 and into the engine induction system downstream of the throttle valve.

Due to the relatively open flow path for ventilating air through filter element 33 and the restriction to flow offered by orifice 54, the pressure at openings 43 never drops more than slightly below atmospheric. If this were not the case, it would be possible for crankcase vapors to be drawn into the induction system by the vacuum in the intake manifold even though the crankcase was not pressurized. This could cause an undesirable reversal of air fiow in tubular connecting means 26, 28, 36 allowing the admission of unfiltered air to the engine crankcase. This is prevented, first, by the restriction of fitting 54 and, second, by tht provision of restricting orifices 46 which insure that except when a positive crankcase pressure exists, the flow through tubular means 50 comes from atmosphere rather than from the crankcase.

From the foregoing description, the present invention is seen to provide a crankcase ventilation system having a large unrestricted passage for the fiow of crankcase vapors into the induction system and arranged to prevent the passage of unfiltered air into the engine crankcase or the engine cylinders without the addition of flow restricting valves to the flow passages of the system. The elimination of such valves in the present system will provide more trouble-free operation and reduce or eliminate maintenance as well as permitting the disposal of larger amounts of crankcase vapors. Provision is made for fresh air filtratration of the crankcase under normal conditions while the fresh air inlet serves as an additional path for the escape of crankcase vapors during periods of excessive blowby when the crankcase becomes pressurized. Crankcase vapors escaping into the fresh air inlet are carried into the induction system downstream of the throttling means along with a continuous stream of fresh air and thus are prevented from escaping to atmosphere.

Although the invention has been described in a particular embodiment, it should be obvious that numerous changes might be made within the spirit of the invention. For instance, tubular means 26, 28, 30 might be connected to any suitable portion of the engine crankcase or its connecting passages and to any suitable portion of the induction system upstream of the throttle means. By the same token, connecting means 50, 52, 54 could be connected to any portion of the system downstream of the throttle means. Also, the restricting means could include only a single orifice 46 or any number of orifices of suitable size to provide the proper restriction to flow from the crankcase into the induction system so that undesired back flow will be prevented, except when the crankcase is pressurized. If desired, a one-way valve means could be included to provide, in conjunction with orifice 46, for decreased restriction to fresh air flow into the crankcase as opposed to fiow of crankcase vapors therefrom. These and other changes which could be made without departing from the spirit of the invention are intended to be considered as a part of the invention which is to be limited only by the language of the appended claims.

I claim:

1. For use with an internal combustion engine having a crankcase and an induction system including throttling means, a crankcase ventilation system comprising conduit means connecting the crankcase with the induction system upstream of the throttling means to carry crankcase vapors to the induction system and inlet means on said crankcase to admit ventilating air thereto, said inlet means being connected with the induction system downstream of the throttling means whereby excess crankcase vapors escaping into said inlet means will be drawn into the induction system.

2. The system of claim 1 wherein said inlet means includes flow restricting means between the crankcase and said induction system connection to limit the flow of crankcase vapors through said inlet means, said induction system connection including second flow restricting means to limit fluid fiow therethrough into the induction system.

3. For use with an internal combustion engine having a crankcase and an induction system including throttling means, a crankcase ventilation system comprising first conduit means connecting the crankcase with the induction system upstream of the throttling means, fresh air inlet means on the crankcase,

second conduit means connecting said inlet means with the induction system downstream of the throttling means, said second conduit means including a restricting orifice to control fiuid flow through said second conduit means and flow restricting means in said inlet means between the crankcase and said second conduit means to prevent the drawing of crankcase vapors from said crankcase through said second conduit means whenever crankcase pressure is below atmospheric.

4. The system of claim 3 wherein said fresh air inlet means comprises a lubricating oil fill tube carrying a breather cap having an annular filter element to prevent dirt from entering the system and an annular gasket seating against the periphery of said oil fill tube between the crankcase and said second connecting means, said flow restricting means comprising a cup shaped member having open and closed ends removably attached with its open end against said breather cap and seated against said gasket at its closed end, said closed end having at least one orifice therethrough, said orifice being appropriately sized to permit an adequate flow of ventilating air into the crankcase but relatively small in comparison with the size of the openings in the fresh air inlet to prevent the drawing of crankcase vapors from the crankcase except when a positive crankcase pressure exists.

5. In an internal combustion engine having a crankcase and an induction system including throttling means, a crankcase ventilation system comprising first means connecting the crankcase with the induction system upstream of the throttling means and second means connecting the crankcase with the induction system downstream of the throttling means, said second connecting means including inlet means to admit air between the crankcase and the induction system,

first flow restricting means between said inlet means and the induction system to limit fluid fiow from said second connecting means into the induction system and second flow restricting means between said inlet means and the crankcase to limit fluid flow therethrough whereby ventilating air is normally drawn into said inlet means and through said second flow restricting means into the crankcase where it mixes with vapors therein and is drawn therefrom through said first connecting means and into the induction system, but excess crankcase vapors can escape through said second flow restricting means and be carried with fresh air from said inlet means through said first flow restricting means and into the induction system.

6. The combination of claim 5 wherein the induction system includes air filtration means upstream of the throttling means and said inlet means includes air filtration means, both said air filtration means together acting to prevent the admission of unfiltered air into the induction system and into the engine crankcase.

7. For use with an internal combustion engine having a crankcase and an induction system including throttling means and air filtration means upstream of the throttling means, a crankcase ventilation system comprising conduit means connecting the crankcase with the induction system upstream of the filtration means to carry crankcase vapors to the induction system,

inlet means on said crankcase to admit ventilating air thereto, said inlet means being connected with the induction system downstream of the throttling means whereby excess crankcase vapors escaping into said inlet means will be drawn into the induction system and air filtration means on said inlet means, both said air filtration means together acting to prevent the admission of unfiltered air to the induction system and to the engine crankcase.

References Cited by the Examiner UNITED STATES PATENTS MARK NEWMAN, Primary Examiner.

A. L. SMITH, Assistant Examiner. 

1. FOR USE WITH AN INTERNAL COMBUSTION ENGINE HAVING A CRANKCASE AND AN INDUCTION SYSTEM INCLUDING THROTTLING MEANS, A CRANKCASE VENTILATION SYSTEM COMPRISING CONDUIT MEANS CONNECTING THE CRANKCASE WITH THE INDUCTION SYSTEM UPSTREAM OF THE THROTTLING MEANS TO CARRY CRANKCASE VAPORS TO THE INDUCTION SYSTEM AND INLET MEANS ON SAID CRANKCASE TO ADMIT VENTILATING AIR THERETO, SAID INLET MEANS BEING CONNECTED WITH THE INDUCTION SYSTEM DOWNSTREAM OF THE THROTTLING MEANS WHEREBY EXCESS CRANKCASE VAPORS ESCAPING INTO SAID INLET MEANS WILL BE DRAWN INTO THE INDUCTION SYSTEM. 